13 research outputs found
Inclusive pentaquark and strange baryons production in pp and \Sigma p collisions at high energy
We calculate the cross sections for the inclusive production in the
fragmentation region of and in collisions
and in collisions at high energy using the - and
-meson exchange diagrams, respectively. The contributions of these
diagrams survive at asymptotically large energies and are energy independent in
this region up to logarithmic and power corrections. We find that inclusive
production should be at the level of 1
MeV. The ratio of the
over the yields is found to be . The
fraction of yields in and collisions is that quantitatively agrees with the preliminary result of the Fermilab
fixed target experiment E781.Comment: 5 pages, 5 figures, 1 table; RevTeX
Pentaquarks in string dynamics
The masses of , , and pentaquarks are
evaluated in a framework of both the Effective Hamiltonian approach to QCD and
spinless Salpeter using the Jaffe-Wilczek diquark approximation and the string
interaction for the diquark-diquark-antiquark system. The masses of the light
pentaquarks are found to be in the region above 2 GeV. The similar calculations
yield the mass of pentaquark 3250 MeV and
pentaquark 6509 MeV.Comment: 5 pages. Based on talk by I.M.Narodetskii at BEACH 2004, 6th
International Conference on Hyperons, Charm and Beauty Hadrons, Illionois
Institute of Technology, Chicago, June. 27 - July 3, 2004. Typos correcte
Tetraquarks and Pentaquarks in String Models
We consider the production and decay of multiquark systems in the framework
of string models where the hadron structure is determined by valence quarks
together with string junctions. We show that the low mass multiquark resonances
can be very narrow.Comment: 7 pages, 2 figure
Pentaquark spectrum in string dynamics
The masses of and pentaquarks are evaluated in a
framework of the Effective Hamiltonian approach to QCD using the Jaffe-Wilczek
approximation. The mass of the state is found to
be MeV higher than the observed mass.Comment: 6 pages, 1 figure included, LaTeX2e; several references added;
misprints corrected; to appear in Physics Letters
Spectrum of the Y=2 Pentaquarks
By assuming a mass formula for the spectrum of the Y=2 pentaquarks, where the
chromo-magnetic interaction plays a main role, and identifying the lightest
state with the Theta^+(1540), we predict a spectrum in good agreement with the
few I=0 and I=1 candidates proposed in the past.Comment: 12 pages, 4 figures, LaTe
Some (further) Comments on the Theta(1540) Pentaquark
Additional broader I=0 states in the KN channel near (1540) are
expected in many models, making the absence of any signature in the
K-deuteron scattering data even more puzzling.
In an ideal "three-body" picture the is viewed as two compact
ud(1)ud(2) color diquarks and an quark. A "QCD-type"
inequality involving , the mass of the L=1 excitation and that of a new I=0 tetraquark vector meson then follows.
The inequality suggests a very light new vector meson, and is violated.
We note that "associated production" of the pentaquark with another
quadriquark or anti-pentaquark may be favored. This along with some estimates
of the actual production cross sections suggest that the can be found
in BaBar or Belle e-e colliders.Comment: 6 page
One-loop corrections to the metastable vacuum decay
We evaluate the one-loop prefactor in the false vacuum decay rate in a theory
of a self interacting scalar field in 3+1 dimensions. We use a numerical
method, established some time ago, which is based on a well-known theorem on
functional determinants. The proper handling of zero modes and of
renormalization is discussed. The numerical results in particular show that
quantum corrections become smaller away from the thin-wall case. In the
thin-wall limit the numerical results are found to join into those obtained by
a gradient expansion.Comment: 31 pages, 7 figure
A Naturally Narrow Positive Parity Theta^+
We present a consistent color-flavor-spin-orbital wave function for a
positive parity Theta^+ that naturally explains the observed narrowness of the
state. The wave function is totally symmetric in its flavor-spin part and
totally antisymmetric in its color-orbital part. If flavor-spin interactions
dominate, this wave function renders the positive parity Theta^+ lighter than
its negative parity counterpart. We consider decays of the Theta^+ and compute
the overlap of this state with the kinematically allowed final states. Our
results are numerically small. We note that dynamical correlations between
quarks are not necessary to obtain narrow pentaquark widths.Comment: 10 pages, 1 figure, Revtex4, two-column format, version to be
published in Phys. Rev. D, includes numerical estimates of decay width
Magnetic Moment of The Pentaquark State
We have calculated the magnetic moment of the recently observed
pentaquark in the framework of the light cone QCD sum rules using the photon
distribution amplitudes. We find that ,
which is quite small. We also compare our result with predictions of other
groups.Comment: 1 eps figure, 13 page
The theta^+ baryon in soliton models: large Nc QCD and the validity of rigid-rotor quantization
A light collective theta+ baryon state (with strangeness +1) was predicted
via rigid-rotor collective quantization of SU(3) chiral soliton models. This
paper explores the validity of this treatment. A number of rather general
analyses suggest that predictions of exotic baryon properties based on this
approximation do not follow from large Nc QCD. These include an analysis of the
baryon's width, a comparison of the predictions with general large Nc
consistency conditions of the Gervais-Sakita-Dashen-Manohar type; an
application of the technique to QCD in the limit where the quarks are heavy; a
comparison of this method with the vibration approach of Callan and Klebanov;
and the 1/Nc scaling of the excitation energy. It is suggested that the origin
of the problem lies in an implicit assumption in the that the collective motion
is orthogonal to vibrational motion. While true for non-exotic motion, the
Wess-Zumino term induces mixing at leading order between collective and
vibrational motion with exotic quantum numbers. This suggests that successful
phenomenological predictions of theta+ properties based on rigid-rotor
quantization were accidental.Comment: 19 pages; A shorter more readable versio